volvo s60 t5 low power

Hello I have a Volvo s60 T5 with a Bsr Stage 1 chiptuning on 300 hp as well as a medium silencer atrappe and open sport exhaust from Ulter. The volvo also has powerful power and drives 260 kmh but at the lower speeds it is really very sluggish. Not even if you start with full throttle at a traffic light spin the wheels through only when it rains so at 20 kmh and I just wanted to ask if the T5 is just translated like that or if my has anything. What brutal to me rken is when it’s warm so 25 degrees it has really noticeably less power it goes best at 12 degrees and rain. I’m thinking now if I install a larger load air cooler. Important info it’s an automatic vehicle but even with dtc from no spinning wheels Vlt you can help me further.